My thinking is things they can easily grab from the backseat and eat while driving. I'd think sandwiches that won't drip or leak fillings. Avocado on any sandwich always makes me happy. Or a spicy nut mix to snack on during the drive would be nice.

fried chicken? sandwiches are always easy to eat on the road. I also on occasion make containers with cut up meat, cheese, crackers and grapes. Kind of like a grown-up lunchable if you will :) Pita pockets stuffed with sandwich fillings would be good too :)

Not sure how fancy you want to go but we pack a simple car/truck picnic for every Sat lunch for my boys for our way home from class. We tend to be more simplistic but here are some ideas: grapes (off the vine, cleaned, so ready to eat directly out of the container), chopped up (large chunks) fresh strawberries, cheese sticks, carrot sticks, mini muffins or cupcakes or something like banana bread slices/squares. As for the "main dish" that is more difficult as we normally do PB & J since those are easy to eat and not messy. Cooked, chunked chicken breast would be good. Or if you are wanting to go a little fancier, maybe a container with a bunch of different sliced meats (salami, pepperoni, etc.) as well as a separate container with a bunch of different cheeses and then maybe some fresh sliced baquette.